The present invention generally relates to a system of liquid ring devices for use in applications such as heat engines, heat pumps and pressure swing adsorption (PSA). In particular, the liquid ring system comprises a casing containing a liquid, a rotor mounted inside the casing and comprising at least one impeller, a liquid ring formed by rotation of the rotor or the casing, a plurality of gas cells formed between the inner surface of the liquid ring and vanes of the impeller, and a fluid connection for example between at least one compressing gas cell and at least one expanding gas cell, integrated with the rotor.
The liquid ring device is known in the prior art, with the principle existing as early as in U.S. Pat. No. 953,222 to Nash in 1910. The first application of the device was found in U.S. Pat. No. 1,094,919 to Nash in 1914 that disclosed a turbo-displacement engine based on a liquid ring device. Thus far, a number of developments based on liquid ring systems have been disclosed, with more than 400 US patents being issued for various applications, such as heat engines, heat pumps and gas compressors.
Generally, a liquid ring device comprises a casing, a rotating vaned impeller eccentrically located within the casing, an inlet port for a gas supply in the end of the casing and an outlet port for a gas discharge in the other end of the casing. During the operation, a liquid is fed into the casing and, due to the rotation of the impeller, the liquid forms a liquid ring against the inside wall of the casing. The gas is trapped within cells formed between the vanes of the impeller and the surface of the liquid, and as a result of the impeller rotation and the eccentricity between the impeller rotation axis and the casing axis, the gas volume in the cells is alternatively reduced and enlarged, which causes compression and expansion of the gas.
Current applications of the liquid ring system mainly include vacuum pumps and gas compressors. The Stirling engine is advantageous in that any type of liquid fuel can be used in the engine; however, an expensive cost of construction, a complex design and a short interval of service (e.g., due to sealing overhauls) are considered as drawbacks of the conventional Stirling engines.
The liquid ring system according to the present invention can be applied to Stirling engines as well as other heat engines, such as Rankin engines, Brayton engines, open-cycle Stirling engines, and for PSA applications, with fewer moving parts compared to the conventional Stirling engines and with liquids as sealings. Thus, a longer interval of service can be achieved. Further, the liquid ring system of the present invention facilitates the use of a liquid salt as the liquid ring, which provides for an increased efficiency compared to the conventional liquid ring system.